1. Field of the Invention
This invention relates to an improvement in oil film bearings of the type employed to rotatably support the journal surfaces of roll necks in a rolling mill.
2. Description of the Prior Art
In the typical rolling mill oil film bearing, as depicted somewhat diagrammatically in FIGS. 1 and 2, the roll 10 has a neck section 12. The neck section 12 may be conical, as shown in FIG. 1, or it may be cylindrical. A sleeve 14 is received on and fixed relative to the neck section 12. The exterior of the sleeve defines the journal surface 16 of the roll neck. A bushing 18 has an internal bearing surface 20 surrounding and rotatably supporting the journal surface 16. The bushing is contained by and fixed within a chock 22. The chock is closed at the outboard end by an end plate 24 and cover 26. A seal assembly 28 is provided between the roll and the inboard end of the chock 22.
During normal operation of the mill, when the roll is rotating at adequate speeds for full hydrodynamic operation, a continuous flow of oil is fed through one of the sets of passageways 29 in the chock, feed openings 30 in the bushing and rebores 32 in the bearing surface 20. From here, the oil enters between the bearing surface 20 and the rotating journal surface 16 to form a hydrodynamically-maintained somewhat wedge-shaped oil film 34 at the bearing load zone "Z". The load zone is located on the side opposite to that of the load "L" being applied to the roll, and the pressure profile at the load zone is schematically depicted in FIG. 1 at "P".
Although not shown, it will be understood that in most cases conventional hydrostatic means are employed to create the necessary oil film between the journal and bearing surfaces when the roll is either not rotating or rotating at a speed slower than that required to create and maintain the hydrodynamic oil film 34.
Oil is continuously drained from between the journal and bearing surfaces 16,20 at both the inboard and outboard ends of the load zone. The oil draining from the inboard end enters an inboard sump 36 enclosed by the seal assembly 28 and the adjacent surfaces of the chock, bushing and roll. Oil draining from the outboard end enters an outboard sump 38 enclosed by the end plate 24 and chock 22. The sumps 36,38 are interconnected by one or more passageways 40 drilled through the chock, and the outboard sump 38 is connected to a conventional lubrication system (not shown) which filters, cools and recirculates the oil back to the bearing for reintroduction between the bearing and journal surfaces 16,20.
It is to be understood that as herein employed, the term "oil" is to be interpreted broadly to include all classes of lubricants employed in bearings of the type under consideration, including for example mineral oil, synthetic oils and mixtures of oils and oil additives.
One of the objectives of the present invention is to achieve an increase in the stiffness of the above described oil film bearing. As herein employed, the term "stiffness" means the ability of the bearing to resist movement of the journal surface 16 relative to the bearing surface 20 in response to the application of the load L to the roll.
Another objective of the present invention is to reduce operating temperatures retained on the roll neck by an interference fit, e.g., by increasing the volume of oil flowing through the bearing. A companion objective is to achieve a reduction in the volume of oil draining into the inboard sump 36, thereby lessening the possibility of oil being lost through the seal assembly 28 as it undergoes normal wear.
Another objective of the present invention is to improve the ability of the bushing and chock to self-align themselves with respect to the journal surface of the sleeve as the roll undergoes deflection during loading.
Another objective of the present invention is to employ multiple axially aligned sleeves which are retained on the roll neck by an interference fit, e.g., by heat shrinking or pressing onto the roll neck.
Still another objective of the present invention is to provide improved means for monitoring the thickness of the hydrodynamically-maintained oil film by measuring the spatial relationship between the journal and bearing surfaces at the center of the load zone.
A still further objective of the present invention is to provide an improved means for monitoring oil temperature at the center of the load zone.